1. Field of the Invention
The invention relates to a TV encoder and, more particularly, to a TV encoder with a function of adjusting hue.
2. Description of the Related Art
A conventional video signal generator device, such as a DVD player, includes a hue processor and a TV encoder, both of which are coupled together through a linear transformation circuit. The linear transformation circuit performs arithmetic operations of linear transformation on a set of hue components of the video signal output from the hue processor such that another set of hue components is input into the TV encoder for encoding.
FIG. 1 is a circuit block diagram showing a portion of a conventional video signal generator device 1. Referring to FIG. 1, the conventional video signal generator device 1 includes a hue processor 10, a linear transformation circuit 11, and a TV encoder 12. First, a set of color mixture signals Cb and Cr representative of hue components of a video signal are changed through the hue processor 10 into another set of color mixture signals Cb′ and Cr′ with adjusted hue. Subsequently, the color mixture signals Cb′ and Cr′ are subjected to arithmetic operations of linear transformation through the linear transformation circuit 11 and then transformed into still another set of color mixture signals U and V. Finally, the color mixture signals U and V are encoded in the TV encoder 12 so as to be output as color mixture signals Cp and Cn. The operations of the conventional hue processor 10, linear transformation circuit 11, and TV encoder 12 will be described in detail hereinafter with reference to FIGS. 2(a) to 2(c).
FIG. 2(a) is a detailed circuit diagram showing the hue processor 10 of the conventional video signal generator device 1 shown in FIG. 1. Referring to FIG. 2(a), in addition to a level-shifting signal Sv, the color mixture signals Cb and Cr are input into adder circuits 101 and 102, respectively. The adder circuit 101 outputs a difference Cb−Sv between the color mixture signal Cb and the level-shifting signal Sv while the adder circuit 102 outputs a difference Cr−Sv between the color mixture signal Cr and the level-shifting signal Sv. The level-shifting signal Sv is adopted to adjust the range of corresponding levels of the color mixture signals Cb and Cr. A sin-cos generator 103 outputs a sin signal sin(X) and a cos signal cos(X) of an adjusting angle X which is adopted to change the hue determined by the color mixture signals Cb and Cr. The signal Cb−Sv is multiplied by the cos signal cos(X) and sin signal sin(X) through multiplier circuits 104 and 105, respectively, so as to be output as signals (Cb−Sv)cos(X) and (Cb−Sv) sin(X). The signal Cr−Sv is multiplied by the cos signal cos(X) and sin signal sin(X) through multiplier circuits 106 and 107, respectively, so as to be output as signals (Cr−Sv)cos(X) and (Cr−Sv) sin(X). The signal (Cb−Sv)cos(X) is added with the signal (Cr−Sv) sin(X) through an adder circuit 108 and then is added with the level-shifting signal Sv through an adder circuit 109 so as to be output as a signal (Cb−Sv)cos(X)+(Cr−Sv) sin(X)+Sv, which is hereinafter referred to as a signal Cb′. On the other hand, the signal (Cr−Sv)cos(X) is subtracted from the signal (Cb−Sv) sin(X) through an adder circuit 110 and then is added with the level-shifting signal Sv through an adder circuit 111 so as to be output as a signal (Cr−Sv)cos(X)−(Cb−Sv) sin(X)+Sv, which is hereinafter referred to as a signal Cr′. To sum up, the operations shown in FIG. 2(a) can be represented as the following equation:                               [                                                                      Cb                  ′                                                                                                      Cr                  ′                                                              ]                =                                            [                                                                                          cos                      ⁢                                                                                           ⁢                      X                                                                                                  sin                      ⁢                                                                                           ⁢                      X                                                                                                                                                          -                        sin                                            ⁢                                                                                           ⁢                      X                                                                                                  cos                      ⁢                                                                                           ⁢                      X                                                                                  ]                        ⁡                          [                                                                                          Cb                      -                      Sv                                                                                                                                  Cr                      -                      Sv                                                                                  ]                                +                      [                                                            Sv                                                                              Sv                                                      ]                                              (        1        )            
FIG. 2(b) is a detailed circuit diagram showing the linear transformation circuit 11 of the conventional video signal generator device 1 shown in FIG. 1. Referring to FIG. 2(b), the signal Cb′ is subtracted from the level-shifting signal Sv through an adder circuit 112 and then is multiplied by a first linear transformation constant K1 through a multiplier circuit 113 so as to be output as a signal (Cb′−Sv)×K1, which is hereinafter referred to as a signal U. On the other hand, the signal Cr′ is subtracted from the level-shifting signal Sv through an adder circuit 114 and then is multiplied by a second linear transformation constant K2 through a multiplier circuit 115 so as to be output as a signal (Cr′−Sv)×K2, which is hereinafter referred to as a signal V. To sum up, the operations shown in FIG. 2(b) can be represented as the following equation:                               [                                                    U                                                                    V                                              ]                =                              [                                                            K1                                                  0                                                                              0                                                  K2                                                      ]                    ⁡                      [                                                                                                      Cb                      ′                                        -                    Sv                                                                                                                                          Cr                      ′                                        -                    Sv                                                                        ]                                              (        2        )            
FIG. 2(c) is a detailed circuit diagram showing the TV encoder 12 of the conventional video signal generator device 1 shown in FIG. 1. Referring to FIG. 2(c), a multiplexor 116 alternately outputs the signal V and its inverted signal −V. A sin-cos generator 117 outputs a sin signal sin(ωt) and a cos signal cos(ωt) wherein ω is a carrier frequency and t is time. The signal U is multiplied by the sin signal sin(ωt) so as to be output as a signal U×sin(ωt). On the other hand, the signals V and −V are alternately multiplied by the cos signal cos(ωt) through a multiplier circuit 119 so as to be output alternately as signals V×cos(ωt) and −V×cos(ωt). Finally, through an adder circuit 120, the signal U×sin(ωt) is alternately added with the signals V×cos(ωt) and −V×cos(ωt) so as to be output alternately as signals U×sin(ωt)+V×cos(ωt) and U×sin(ωt)−V×cos(ωt), which are hereinafter referred to as signals Cp and Cn, respectively. To sum up, the operations shown in FIG. 2(c) can be represented as the following equation:                               [                                                    Cp                                                                    Cn                                              ]                =                              [                                                                                sin                    ⁡                                          (                                              ω                        ⁢                                                                                                   ⁢                        t                                            )                                                                                                            cos                    ⁡                                          (                                              ω                        ⁢                                                                                                   ⁢                        t                                            )                                                                                                                                        sin                    ⁡                                          (                                              ω                        ⁢                                                                                                   ⁢                        t                                            )                                                                                                            -                                          cos                      ⁡                                              (                                                  ω                          ⁢                                                                                                           ⁢                          t                                                )                                                                                                                  ]                    ⁡                      [                                                            U                                                                              V                                                      ]                                              (        3        )            